The following enzymes involved in the metabolism of the prostaglandins will be measured in tissues and in body fluids: prostaglandin synthetase, 15-hydroxy-PGF 2 alpha dehydrogenase, 15-keto-PGF 2 alpha (delta 13,14) reductase, PGE-9-keto reductase, PGE dehydrase, and PGA isomerase. The prostaglandin synthetase system will also be measured in various tissues. All of these enzymes will be measured with antibodies directed specifically toward the substrate and/or the product of the appropriate enzymatic reaction. The various classes of prostaglandins and their metabolites will also be measured in tissues and in body fluids. Many of the enzymes mentioned above will be purified and characterized. Serological means will be used to compare enzymes with a common function from different organs.